This is a multicenter double-blind, ... study of methylphenidate (Ritalin), clonidine (Catapres), and combined methylphenidate and clonidine (2x2 factorial design) for children with both ADHA and chronic tics. The study will address the following aims: to determine the efficacy of the 2 drugs used alone or in combination for the symptoms of ADHD and to determine the influence of the 2 drugs alone or in combination on the severity of tics in children with chronic tics.